Twin lens parallax free camera system

ABSTRACT

A camera system having a picture taking lens and a view finder lens positioned at some suitable angle to each other and a reflector positioned between the lenses at an angle bisecting the angle formed with respect to a line through the center of each lens used as a means of focusing the camera system and movable out of the path of the picture taking lens before actuation of the camera shutter.

Matted States Swarm atent [541- 'TWHNLENS PARALLAX FRE CAMERA SYSTEM[72] Inventor: Carl C. Swarm, 1334 Belmeade Forest, Kingsport, Tenn.37664 [22] Filed: .Mar.9, 1970 [21] Appl. No.: 17,548

[56] References Cited UNITED STATES PATENTS I 2,153,892 4/1939 Jackman..95/12.20 ux [15] 3,653,314 [451 Apr. 4, 1972 2,530,793 11/1950 Thomas..95/18X 852,476 5/1907 Verbeck.. ....95/l8 1,733,511 10/1929 Mueller..95/44 Primary Examiner-Samuel Sl Matthews Assistant Examiner-Robert P.Greiner Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT Acamera system having a picture taking lens and a view "finder lenspositioned at some suitable angle to each other and a reflectorpositioned between the lenses at an angle bisecting the angle formedwith respect to a line through the center of each' lens used as a meansof focusing the camera system and movable out of the path of the picturetaking lens before actuation of the camera shutter.

9 Claims, 3 Drawing Figures Ptent ed April 4, 1972 2 Sheets-Sheet 1INVENTOR CARL c SWANN ATTORNEYQ Patented April 4, 1972 3,653,314

2 Sheets-Sheet 2 INVENTOR CARL C. SWANN ATTORNEYS.

1. TWIN LENS PARALLAX FREE CAMERA SYSTEM BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to a camera system havinga separate view finder lens and a picture taking lens which can takepictures having no parallax. Y

2. Description of the Prior Art The heretofore unsolved problem oftaking photographic pictures having absolutely no parallax is well knowninthe art of photography. This problem is peculiar to cameras whichutilize two lenses, one lens of which serves as the view finder lens andthe other of which serves as the picture taking lens. Parallax simplystated is the angular displacement or shift when the object is viewedfirst through the view finding lens and then is viewed through thepicture taking lens. The

phenomena of parallax results from the fact that since the; picturetaking lens are separated by a view finding lens and the distance, acommon center line cannot exist between the view finder lens and thepicture taking lens.

The problem of parallax does not exist when a single lens is used whichserves as both the picture taking lens as well as the view finding lens.One such camera is the basic view type camera which has a front standardhaving a single lens, a back standard having a ground glass focusingscreen and means for accepting a film holder and a bellows connectingthe front and back standards. The basic view type camera is used forfine portraiture, commercial and architectural photography because theexact image shown on the ground glass will be that photographed. Thesebasic view cameras have numerous drawbacks in that they are slow inoperation in that after the subject to be photographed has been framedon the focusing screen, the shutter must be closed, set and cocked, afilm holder must be inserted and the dark slide removed before theshutter can be released to complete the exposure.

Another type of camera is that of the reflex type wherein a single lensserves as both the view finding lens and the picture taking lens. Thereflex type camera employs a mirror which is positioned between thecamera lens and the film and focal plane shutter to reflect the subjectto be photographed to a viewing screen. After the subject has beenframed in the viewing screen the mirror is moved out of the path of theshutter just before the shutter is opened to take the picture. Thereflex type camera is less bulky than the basic view type camera,however, the noise and time lag associated with the mechanisms whichmust operate before the opening of the shutter is considerable and verydistracting which in larger format cameras is intolerable.

A further type of camera is the twin lens reflex type which has definiteadvantages in that, with the subject in the appropriate position, thelights and exposure evaluated, the shutter may then be set and cockedand the diaphragm adjusted on the taking lens, before composing andfocusing the subject on the ground glass viewing screen through thealways open focusing lens. However, these twin lens reflex cameras havethe disadvantage of accute parallax especially when used for extremecloseup work where the subject may be completely missed by the takinglens or have a definitely different perspective or point of view eventhough it is apparently properly framed and composed on the focusingscreen.

The twin lens camera system of the present invention eliminates thedisadvantages of theaforementioned camera systems while at the same timeproviding a camera which is inexpensive to manufacture and which can beused for both closeup as well as distant photography without the seriousproblem of parallax being present.

SUMMARY OF THE INVENTION back standard containing the photographic filmis connected to the front standard by means of a bellows and is movablewith respect to the front standard as the camera is focused. A secondlens, the view finder lens, is mounted on the front standard such thatthe central axis of the view finder lens is perpendicular to the centralaxis of the picture taking lens. A focusing screen is positioned abovethe back standard and moves with it. A plane parallel to the front ofthe focusing screen is also perpendicular to the center line through thepicture taking lens. A front surface mirror or other like reflectingdevice is positioned through the intersecting point of the center linesof the picture taking and view finding lenses at a 45 angle with respectto both of these center lines. An additional front surface mirror ispositioned behind the view finding lens to thereby reflect the lightpassing through the image finding lens to the focusing screen. Inasmuchas the focal length of both the picture taking lens and the view findinglens is the same, the distance between the focal point of the picturetaking lens to the surface of the photographic film will be identical tothe distance between the focal point of the view finding lens to thesurface of the focusing screen via the mirror because the back standardand the focusing screen move as one during focusing of the camera.

During the focusing operation of the camera, the reflecting surfacepositioned between the view finding and picture taking lenses is at anangle of 45 with respect to the central axis of both of the lenses. Thelight from the subject and object to be photographed is reflected fromthis surface through the focusing lens to the mirror behind it and fromthere to the focusing screen. At the instant the proper composition andthe focus are obtained on the focusing screen (assuming the picturetaking lens and shutter adjustments having been preset), the reflectingsurface between the picture taking lens and view finding lens is movedout of the path of the picture taking lens by any suitable means and thefilm is exposed. The picture taken is identical to the subject matterframed on the focusing screen and has no parallax.

A second embodiment of the present invention eliminates the necessity ofusing the reflecting surface positioned between the view finding lensand the focusing screen. The picture taking lens and viewfinding lensare positioned at a suitable angle with respect to each other in thesame manner as the same lenses in the preferred embodiment. The frontand back standards which hold the picture taking lens and photographicfilm respectively are connected by means of a conventional bellows asare the front standard and back standard which contain the view findinglens and focusing screen respectively. The back standard containing thephotographic film and the back standard containing the focusing screenare both moved toward and away from their respective front standards thesame amount during the focusing operations so that the distance betweenthe focal point of the picture taking lens and the surface of the filmis always the same as the distance between the focal point of the viewfinding lens and the focusing screen when lenses having the same focallength are used as both picture taking lens and the view finding lens.The second embodiment does, however, lend itself more readily to the useof a picture taking lens having a focal length different from that ofthe view finding lens as long as the distances between the focal pointof the picture taking lens and the surface of the photographic film iskept proportional to the distance between the focal point of. the viewfinding lens and the surface of the focusing screen. This concept alsopermits the use of very short focus lenses.

A third embodiment of the present invention is similar to the secondembodiment. However, the bellows and focusing screen are eliminated anda video or television transmitting tube is positioned behind the viewfinding lens. The video transmitting tube is mounted within a housingand movable conjointly with the back standard holding the photographicfilm. The focal length of the view finding lens and picture taking lensmay be different from each other as in the second embodiment as long asthe distance between the focal point of the picture taking lensand thephotographic film is kept proportional to the distance between the focalpoint of the view finding lens and the signal plate of the videotransmitting tube.

The electrical output signal of the video transmitting tube, whichsignal contains the image as viewed through the view finding lens, isfed to a video or television receiver for viewing. The video receiverand its display screen can be mounted in the same housing which containsthe video transmitting tube or it can be set up in a remote location. Ascan be seen, the third embodiment just described readily lends itselfto. closed circuit television viewing or surveilance with the addedfeature that whenever a permanent parallax free record of the area orobject under surveilance is desired, all that need be done is to actuatethe shutter mechanism associated with the picture taking lens to therebyremove the reflecting surface and expose the photographic film. Inaddition, by rapidly mov- The distance between the photographic film 20and the focusing the reflecting surface into and out of the path oflight entering the picture 7 taking lens and by stepping the photographic film in synchronism therewith, a permanent parallax free recordcan be obtained in the form of movie film.

The reflecting device used in all three embodiments which is positionedat an angle to bisect the angle at the intersection of the center linesof the picture. taking and view finding lenses can be a light weightmetallic'front surface mirror which could be rotated, slid or hinged toswing out of the path of the picture taking lens before the shutter isopened. Design of mechanisms for rotating, swinging or sliding thereflecting device into and out of the path of the picture taking lensare too numerous for description in the present application. Thereflecting means could also be a partial mirror or beam splitterrequiring no moving parts which would considerably increase theoperational speed of the camera but would result in a reduction in thetransmission value of both the viewing and exposing light received. Afurther example of a light reflecting means could be devices whichutilize the Kerr magneto-optic or electro-optic effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view,partly in section, of one embodiment of the twin lens camera of thepresent invention; and

FIG. 2 is a side elevation view, partly in section of a secondembodiment of the twin lens camera of the present invention.

FIG. 3 is a side elevation view, partly in section, of a thirdembodiment of the twin lens camera of the present invention.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 sets forth the preferredembodiment of the twin lens parallax free camera system 10 of thepresent invention having a base 12. A front standard 14 is mountedperpendicular to the base 12 and supports a picture taking lens 16. Aback standard 13 is mounted-on the base 12 parallel to the frontstandard 14 and is movable toward and away from the front standard 14 byany suitable means such as a conventional rack and pinion wheel (notshown). The back standard 18 moves a guide track means 19 and supportsthe photographic film 20. The bellows 22 made of cloth or other suitablematerial is positioned between and has its ends secured to the frontstandard l4 and back standard 18, respectively, in order to concentrateall of the light passing through the picture taking lens 16 onto thephotographic film 20. A support member 24 is also mounted on theadjustable back standard 18 and has a focusing screen 26 mountedthereon.

The front standard 14 has a member 28 extending outwardly from andperpendicular to the plane of the front standard 14 for supporting aview finding lens 30. A housing 32 forms a chamber with'the view findinglens support member 28 and the base 12 and encloses the focusing screen26. A mirror 34 is mounted within the housing 32 in order to reflect thelight passing through the view finding lens 30 to the focusing screen26. Inasmuch as the back standard 18 and focusing screen support member24 move together the distance between the photographic film and focusingscreen 26 ing screen 26 is chosen such that the distance (b) between thefocal point 17 of the picture taking lens 16 and the photographic film20 is always equal to the sum of the distances (a) and (c) between thefocal point 31 of lens 30, the surface of the mirror 34, and thefocusing screen 26 during the focusing and picture taking operation ofthe camera.

A reflecting surface 36 is movably mounted between the picture takinglens 16 and the view finding lens 30 at a 45 angle with respect to botha center line through the focal point 17 of the picture taking lens 16normal to the photographic film 20 and a center line through the focalpoint 31 of view finding lens 30, parallel to the focusing screen 26.The reflecting surface 36 is movable from the solid line position whereit passes through the intersection of the aforementioned center lines tothe phantom line position by any suitable means shown generally at 38 aninstant before the shutter of lens 16 (not shown) is actuated.

The operation of the camera system set forth in FIG. 1 will now bedescribed. Before attempting to focus the camera, the

reflecting surface 361s cocked to the solid line position wherein bequals 0 and the light from the subject to be'photographed is reflectedoff of the reflecting surface 36 through the view finding lens 30 to themirror 34 and from there to the focusing screen 26. Actuating means 38can be connected to the camera shutter by any suitable means (not shown)such that when the reflecting surface 36 is moved to the solid lineposition between the lenses l6 and 30, the shutter of the camera is alsococked. The focusing screen 26 is then moved back and forth until thesubject to be photographed is in focus and framed on the focusingscreen. Movement of the focusing screen 26 also results in movement ofthe photographic film with respect to the picture taking lens 16. Thus,the distance (b) will always be equal to the sum of the distances (a)(0). After the subject to be photographed is in focus, the means 38 isactuated to both move the reflecting surface 36 to the phantom lineposition and to actuate the camera shutter. The light from the subjectto be photographed can now pass directly through the picture taking lens16 to the photographic film 20 and a parallax free picture is taken.

Referring to FIG. 2 which shows a second embodiment of the presentinvention, like numerals will indicate like elements set forth withregard to the embodiment of FIG. 1. The embodiment of FIG. 2 differsfrom the embodiment of FIG. 1 primarily in the fact that the focusingscreen 40 is positioned directly behind the view finding lens 30 at anangle with respect to the surface of the photographic film 20 ratherthan parallel to it as disclosed in FIG. 1.

The focusing screen 40 is connected to the view finding lens supportmember 28 by means of a bellows 42 in the same manner as the backstandard 18 is connected to the front standard 14 by means of bellows22. The focusing screen 40 is moved toward and away from the viewfinding lens 30 by means of a rack and pinion wheel (not shown) or othersuitable means which also moves the back standard 18 and photographicfilm 20 with respect to the picture taking lens 16 such that thedistance (b) between the focal point 17 of the picture taking lens andthe photographic film 20 is always equal to the distance (b) between thefocal point 31 of the view finding lens 30 and the focusing screen 40.

An additional reflecting mirror 44 is positioned at a 45 angle withrespect to the focusing screen 40 to enable focusing to be accomplishedfrom the same side of the camera as that containing the photographicfilm 20. The reflecting mirror 44 can be eliminated if desired. Theoperation of the camera set forth in the embodiment of FIG. 2 is thesame as that set forth above with respect to the embodiment of FIG. 1.

Referring to FIG. 3 which shows a third embodiment of the presentinvention, again like numerals will indicate like elements set forthwith regard to the embodiments of FIGS. 1 and 2. The embodiment of FIG.3 differs from the embodiment of FIG. 2 in that a housing 46 extendsfrom the view finding lens tube 48 movably mounted therein. The videotransmitting tube 48 is similar to the conventional television cameratubes of the, for example, iconoscope, orthicon, or indicon type. Thevideo transmitting tube 48 has a signal plate 49 which is positionedbehind the view finding lens 30 in a mount 50 which mount is movablewith respect to the view finding lens 30 by means, for, example, of arack and pinion wheel (not shown.) in much the same manner as is thefocusing screen 40 in the embodiment of FIG. 2. The electrical outputsignal of the video transmitting tube 48 contains the image as viewedthrough the view finding lens 30 and this signal is fed by means of acable 51 to either or both a video or a television receiver 52 mountedwithin the-housing 46 having a display screen 54 extending outside thehousing 46 or to a remote video receiver 56 housing a display screen 58.The operation of the camerav set forth in the embodiment of FIG. 3 isthe same as that set forth above with respect to the embodiments ofFIGS. '1 and 2 with the only difference being the video transmittingtube 48 and signal plate 49 are moved with respect to the view findinglens 30 during focusing rather than the focusing screens 26,40.

The reflecting surface 36 in all three embodiments can be a full frontsurface mirror which reflects the full amount of light from the subjectto be photographed to the focusing screen or video transmitting tube butwhich, however, must be moved out of the way of the picture taking lens16 as described above with respect to the embodiment of FIG. 1 beforethe camerashutter is opened. If the reflecting surface 36 is a partialmirror, no movement of the mirror is required inasmuch as some of thelight from the subject passes through the mirror to the taking lens 16and some of the light is reflected to the focusing lens 30. However, ifa partial mirror is used and the transmission value of the mirror isequal to its reflection value, the light available for both focusing andexposing the photographic film will be reduced by at least 50 percent. Abeam splitter could also be used in place of the reflecting mirror 36with the same advantages and disadvantages set forth above with respectto the use of a partial mirror. Additional devices such as those whichemploy the Kerr magneto-optical or electro-optical effect can also beused in place of the reflecting mirror 36. If a partial mirror, beamsplitter or Kerr device is used, it must be positioned such that itbisects the angle formed by the center line through the focal point 17of the picture taking lens 16 and the center line through the focalpoint 311 of the view finding lens 30 at their point of intersectionsuch that the distance (15) is always equal to (b) and the distance (a)equals (a').

It is also possible in all three embodiments of the present invention tohave lenses such that (b) need not be equal to the sum of (a) and (c) orthat (B) need not be equal to (B) as long as the focal lengths of thepicture taking lens 16 and the view finding lens 30 are in properproportion to each other. For example, if the picture taking lens 16 hasa focal length of 6 inches and the view finding lens has a focal lengthof 3 inches, then in the embodiment of FIG, 2 (B) would be equal to 6inches and B would be equal to 3 inches (at infinity focus) and themechanism for moving the focusing screen 40 and photographic film 20would have a 2:1 movement ration. If (B) is extended to 9 inches, then(B') will be-extended to 4% inches. In the foregoing example, thefocusing screen 40 would have half the diametral image size as thatprojected on the photographic film 20. The same would be true for B andB in the embodiment of FIG. 3.

This invention therefore provides a camera system which is simple tooperate, relatively inexpensive to manufacture and which takes parallaxfree pictures.

What is claimed is: g

1. In a camera of the type adapted to contain photographic film, ashutter and picture taking lens means aligned with said film,comprising:

a. film holding means movable with respect to said shutter and picturetaking lens during the focusing of said camera;

b. additional lens means mounted adjacent said picture taking lens meansfor focusing said camera; 0. screen means secured to and movable conointly with said film holding means for focusing the image as receivedthrough said focusing lens whereby movement of the screen means to focusthe image thereon will simultane ously move the film holding means intofocus relative to the picture taking lens; and v d. reflecting meanspositioned between the front of said picture taking lens and. the frontof said focusing lens, said reflecting means having a first state forreflecting light through said focusing lens during the focusingoperation of said camera and a second state to permit light to entersaid picture taking lens during the picture taking operation of saidcamera.

2. A camera system as set forth in claim 1 wherein said screen means forfocusing the image viewed through said focusing lens is parallel to saidphotographic film.

3. In a camera system as set forth in claim 1 wherein said screen meansfor focusing the image viewed through said focusing lens is normal tosaid photographic film.

4. In a camera system as set forth in claim 1 wherein said reflectingmeans is movable between a first position for reflecting light throughsaid focusing lens during the focusing operation of said camera and asecond position for permitting light to enter said picture taking lensduring the picture taking operation of said camera.

5. In a camera system as set forth in claim 1 wherein said reflectingmeans is positioned in the first state at a 45 angle with respect toboth a center line through the focal point of said picture taking lensand a center line through the focal point of said focusing lens.

6. In a camera system as set forth in claim 1 wherein said reflectingmeans in the second state is positioned at an angle other than 45 withrespect to both a center line through the focal point of said picturetaking lens and a center line through the focal point of said focusinglens.

7. In a camera system as set forth in claim 1 wherein said screen meansfurther includes a video transmitting tube means movable conjointly withsaid film holding means for focusing the image as received by said videotransmitting tube means through said focusing lens, said videotransmitting tube means being connected to a video receiving means fordisplaying a video image transmitted by said video transmitting tube.

8. In a camera system as set forth in claim 5 wherein said reflectingmeans is a partial mirror.

9. In a camera system as set forth in claim 5 above wherein saidreflecting means is a beam splitter.

1. In a camera of the type adapted to contain photographic film, ashutter and picture taking lens means aligned with said film,comprising: a. film holding means movable with respect to said shutterand picture taking lens during the focusing of said camera; b.additional lens means mounted adjacent said picture taking lens meansfor focusing said camera; c. screen means secured to and movableconjointly with said film holding means for focusing the image asreceived through said focusing lens whereby movement of the screen meansto focus the image thereon will simultaneously move the film holdingmeans into focus relative to the picture taking lens; and d. reflectingmeans positioned between the front of said picture taking lens and thefront of said focusing lens, said reflecting means having a first statefor reflecting light through said focusing lens during the focusingoperation of said camera and a second state to permit light to entersaid picture taking lens during the picture taking operation of saidcamera.
 2. A camera system as set forth in claim 1 wherein said screenmeans for focusing the image viewed through said focusing lens isparallel to said photographic film.
 3. In a camera system as set forthin claim 1 wherein said screen means for focusing the image viewedthrough said focusing lens is normal to said photographic film.
 4. In acamera system as set forth in claim 1 wherein said reflecting means ismovable between a first position for reflecting light through saidfocusing lens during the focusing operation of said camera and a secondposition for permitting light to enter said picture taking lens duringthe picture taking operation of said camera.
 5. In a camera system asset forth in claim 1 wherein said reflecting means is positioned in thefirst state at a 45* angle with respect to both a center line throughthe focal point of said picture taking lens And a center line throughthe focal point of said focusing lens.
 6. In a camera system as setforth in claim 1 wherein said reflecting means in the second state ispositioned at an angle other than 45* with respect to both a center linethrough the focal point of said picture taking lens and a center linethrough the focal point of said focusing lens.
 7. In a camera system asset forth in claim 1 wherein said screen means further includes a videotransmitting tube means movable conjointly with said film holding meansfor focusing the image as received by said video transmitting tube meansthrough said focusing lens, said video transmitting tube means beingconnected to a video receiving means for displaying a video imagetransmitted by said video transmitting tube.
 8. In a camera system asset forth in claim 5 wherein said reflecting means is a partial mirror.9. In a camera system as set forth in claim 5 above wherein saidreflecting means is a beam splitter.